Heat exchangers are used in the vast majority of motor vehicles that are powered by an internal combustion engine. The heat exchangers are used for engine cooling and passenger compartment heaters. Most heat exchangers include a header and a tank at each end core surface. It has become common practice to manufacture the tank from a plastic material and the header from a heat conductive metal material such as aluminum. The plastic tank is mechanically joined to the header. It is vital that the junction between the tank and header be leak-free and durable in spite of the sometimes corrosive fluid that flows through the heat exchanger. It is also common practice to use elastomeric gaskets in the junction between the tank and header to prevent leakage between the header and tank.
The junction between the tank and header poses a major problem to the durability of the heat exchanger. Usually the junction design has a channel formed in the header to receive edge portions of the tank. An elastomeric gasket is compressed therebetween. In many of these junction designs, a narrow crevice between the tank wall and inner wall of the channel allows fluid to seep therein, but has either limited or no fluid flow therethrough. The narrowness of the crevice prevents the normal washing action of the coolant flow through the crevice. Under certain conditions, particles within the coolant become lodged in the crevice and inside channel section which can initiate crevice corrosion. Eventually, the progression of the crevice corrosion results in a leak in the heat exchanger.
Several efforts have been made to eliminate crevice corrosion. Some of these efforts use extensive redesign of the tank foot to provide flow channels to wash the particles from the inside channel section. Headers have also been manufactured with a zinc alloy or an alloy of aluminum, magnesium and zinc on the inner surfaces exposed to the coolant. These tank foot redesigns and use of the mentioned alloys are expensive attempted corrections but they do not eliminate the basic conditions that instigate crevice corrosion. Both the crevice and the contact of the coolant with the header within the channel remain in these redesigns.
Gaskets have undergone many different designs. Many of these gaskets are used with a tank foot that has a compression rib formed therein. Some gasket designs have been developed with beads to provide sealing forces in the channel. Still other gaskets have been designed to extend into the tank interior. While these gaskets fill the channel and the crevice formed between the tank foot and header channel, they create their own crevices with the header to form other areas of potential corrosion.
What is needed is a gasket with a truncated lip that fills the crevice between the tank foot and inner channel wall but has its distal end under compression between the foot and channel wall so that the coolant is sealed from entering between the gasket and either the header or tank foot.
What is also needed is a sealing gasket that has the convenience of assembly of an 0-ring with increased joint rigidity.